1. Field of the Invention
The present invention relates to an optical printhead used for forming images on a photosensitive recording medium. The present invention further relates to an image forming apparatus including an optical printhead.
2. Description of the Related Art
Recently, digital cameras are more popular than film cameras. As is known, digital cameras are provided with recording medium such as flash memories, so that images are stored in the recording medium as digital data. Such stored digital data is sent to an inkjet printer or thermal-transfer printer to be printed on plain paper. Alternatively, an optical printhead is used to form images on photosensitive films based on the stored digital data. Digital cameras provided with a compact optical print head are also commercially available. With such arrangements, images can be formed on photosensitive films on the spot.
An example of conventional optical printhead is disclosed in JP-A-2000-280527. The printhead shown in the application includes a light source and a liquid crystal shutter. The light source generates linear light extending in a primary scanning direction. The liquid crystal shutter selectively transmits the linear light to illuminate a photosensitive film. The light source includes one or more light-emitting diodes and a transparent light guide. Light emitted from the light-emitting diode is changed to a line of illuminating light by the light guide.
The conventional optical printhead has the following problem. The light from the light-emitting diode undergoes repeated total reflection before emitted out from a light emitting area of the light guide. Thus, the emitted light tends to diffuse while traveling. As a result, only part of the light, emitted from the light emitting area of the light guide, can reach a predetermined linear area on the liquid crystal shutter. In other words, the light from the light-emitting diode cannot be put to efficient use.